Internal combustion engine



April 4, 1939. A. G. M. MICHELL 2,152,811

' INTERNAL COMBUSTION ENGINE Original Filed Nov. 21, 1934 2 Sheets-Sheet 1 INVENTOR vA l 4, 1939, A. G. M. MICHELL 2,152,811

INTERNAL COMBUSTION ENGINE Original Filed Nov. 21, 1934 2 Sheets-Sheet 2 W ATTORNEY Patented Apr. 4, 1939 UNITED STATES,

PATENT OFFICE INTERNAL COMBUSTION ENGINE Anthony George Maldon Michell, Melbourne,

Victoria, Australia 10 Claims.

This invention relates to internal combustion engines in which the ignition of the fuel is effected by compression of the cylinder contents consisting of air together with some residual gases of combustion, and in which the cylinders are arranged parallel to and circumferentially around the engine shaft, the pistons driving the shaft through a swash plate, slant, Z-crank, or similar member attached to the shaft.

It is well known that in compression ignition engines a higher degree of compression is required to effect self-ignition at starting and when the engine is running on light load than is necessary after the engine has attained full load. When, as is usual, the engine is arranged to work with a fixed ratio of compression, constant for all loads, this ratio must be sufficiently high to ensure ignition at starting and the design of the engine must therefore provide greater strength, and consequently involves greater weight and cost than would be necessary if the compression were only suflicient for full load running. The higher compression also results in rougher and more noisy running.

It is the purpose of the present invention to remove or, at least, minimize these disadvantages of the compression ignition engine by providing automatic means for progressively reducing the compression pressures as the engine load increases so as to maintain at full load only such a degree of compression as is then necessary to ensure ignition.

The engine chosen for illustration of the application of the invention is a two-stroke angina of the form described in applicant's copending application, Serial No. '754,039, of which this application is a division, but it is to be understood that the use of the invention is not restricted to this particular form.

In the accompanying drawings,

Fig. 1 is a longitudinal section of the engine; and

Figs. 2 and 3 are half transverse sections taken respectively on the lines II, II and III, III of Fig. 1, theother halves of each of these engine sections being precisely similar to the half which is shown.

In the embodiment of the invention illustrated, the invention is shown as applied to an engine of the swash plate or slant type in which the reciprocating motion of the pistons is transmitted to the engine shaft through a swash plate or slant mounted on the shaft.

In the embodiment of the invention shown, the engine shaft l is fitted with a slant 2, with which the power pistons 3 engage through bridge members 4, fitted with hearing members 5 and 6. This connection between the pistons and the shaft insures a definite, positive and constant relation between the shaft and the pistons and is 5 not varied or adjustable.

On the opposite end of the bridge members 4 from the power pistons 3 are fitted air pistons 1, working in air cylinders 8 which serve for the supply of air to the power cylinders 9 for scav- 10 enging and combustion, according to the method usual in two-stroke engines.

Soavenge ports- Ill and one or more exhaust valves II are provided in each cylinder, these being operated by usual means. In the engine illustrated, auxiliary exhaust ports l2 and exhaust passages l3 are shown, the use of these ports and passages being fully explained in the applicants copending application above men tioned, but not being essential to the present invention.

The engine chosen for illustration has three power cylinders A, B and C, operating in succession in each revolution of the shaft, but the number of cylinders is immaterial to the invention. The shaft I is mounted in the main bearings H in such a manner as to be free to move longitudinally therein, its longitudinal position being determined by the thrust collar l5 which makes working contact, either directly or through pads It or through balls or rollers, with the cylindrical thrust supporting element or abutment I'I.

The abutment I1 is formed with two cylindricalportions l8, l9 fitting respectively the cylindrically bored surfaces 20, 2| in the fixed cylinder head 22, or in a member rigidly secured thereto so as to move freely with a substantially fluid-tight fit therein, and thus forming an annular dash-pot 23 between the surfaces l9 and 40 20. Springs 24 are located in the dash-pot 23 between theabutment l1 and the cylinder head 22, thus supporting the thrust of the engine shaft, and the dash-pot 23 is filled with liquid which may preferably be portion of the oil used for the lubrication of the engine and supplied under pressure by the pump 25.

-A by-pass 26 with needle valve 21 is arranged to make communication between the dash-pot space 23 and a portion of the engine casing from which the liquid can be drained back to the pump 25 so as to control the rate of movement of the abutment I! under the action'of the engine thrust and its return motion under the action of the springs 24.

V pression space being thus reduced to a greater rim The strength and elasticity of the springs 2t and the opening of the needle valve 27 are so arranged that under full load conditions the total pressure of the gases in the power cylinders 9, acting through the pistons 3, bridge member 5 and bearing members 5, slant 2, shaft i and collar IS, the oppositely acting pressures of the air cylinders 8 being usually negligible, is sufficient to overcome the fluid pressure in the dashpot 23 and to compress the springs 24 and retain thev'arious parts in the relative positions shown by full lines in Fig. 1, the phase of the engine revolution shown in this figure being that at which the piston 3 of the cylinder A is at its top dead-center position. The compression space between the piston 3 and the cylinder head is then as great as is compatible with self-ignition of the fuel when the engine is running on full load and consequently warm.

At starting, i. e. before combustion has commenced and under light loads the total pressure of the gases in the cylinders is lower and under these conditions the springs 24 extend and return the parts against the engine thrust until the piston 3 occupies some such position as is shown by dotted lines at 33 in Fig. l, the com.-

or less extent according to the total pressures existing in the cylinders, and the resulting compression pressure sufiiciently raised to ensure ignition under the starting or light load condition existing at any time.

The expression total pressure of the gases hereinbefore used is to be understood as meaning the average total pressure during the engine cycle. oscillatory movements of the parts due to fluctuations of the total pressure from the average during the cycle are to be damped out by regulation of the needle valve 21.

It is to be remarked that the oil pressure in the dash-pot 23, being determined by the viscous resistance of the oil passing through the valve 21, will, other things being equal, diminish as the load on the engine and consequently the temperature of the oil, increase. By this action of the oil supplied by the pump to the dash-pot, the desired result of increasing the compression volumes at the higher engine loads is thereby assisted.

Although one specific embodiment of the invention has been particularly shown and described, it will be understood that the invention is capable of modification and that changes in the construction and in the arrangement of the various cooperating parts may be made without departing from the spirit or scope of the invention, as expressed in the following claims.

What I claim is:

1. In a compression ignition engine having cylinders, pistons and a shaft operatively driven by the pistons, said pistons being disposed in definite, positive and constant longitudinal relation with and imposing a longitudinal load on the engine shaft, mechanism controlled automatically, acting longitudinally on the shaft and by the pressure of the gases in the engine cylinders for moving the pistons and engine shaft longitudinally uniform distances and in unison so as to vary the compression spaces of the cylinders in direct ratio with the average pressures therein, said mechanism including a thrust member on the shaft, a thrust resisting member resiliently supported on the engine frame and engaging said thrust member, and resilient means between the thrust member and the thrust resisting member for moving the shaft and pistons in one direction, the action of said resilient means being controlled by the pressure of the gases in the cylinders.

2. In a compression ignition engine having cylinders, pistons and a shaft operatively driven by the pistons, said pistons being disposed in definite, positive and constant longitudinal relation with and imposing a longitudinal load on the engine shaft, mechanism controlled automatically, acting longitudinally on the shaft and by the pressure of the gases in the engine cylinders for moving the pistons and engine shaft longitudinally uniform distances and in unison so as to vary the compression spaces of the cylinders in direct ratio with the average pressures therein, said mechanism including a thrust member on the shaft, a thrust resisting member engaged by the thrust member and resilient means acting between the thrust member and the thrust resisting member, said thrust resistin member forming the movable element of a dashpot and supported in part, resiliently and in part by the pressure of fluid circulated through the engine and dash-pot, and means for conducting fluid to the dash-pot when the engine is in operation.

3. In a compression ignition engine having cylinders, pistons and a, shaft operatively driven by the pistons, said pistons being disposed in definite, positive and constant longitudinal relation with and imposing a longitudinal load on the engine shaft, mechanism controlled automatically, acting longitudinally on the shaft and by the pressure of the gases in the engine cylinders for moving the pistons and engine shaft longitudinally uniform distances and in unison so as to vary the compression spaces of the cylinders in direct ratio with the average pressures therein, said mechanism including a thrust member on the shaft and a thrust resisting member engaged by the thrust member and resilient and hydraulic means for controlling the operation of said thrust resisting member.

4. In a compression ignition engine having cylinders, pistons and a shaft operatively driven by the pistons, said pistons being disposed in constant, definite and positive longitudinal relation with and imposing a longitudinal load on the engine shaft, mechanism including pressure means acting longitudinally on the shaft and automatically controlled by the pressure of the gases in the engine cylinders for moving the pistons and engine shaft longitudinally uniform distances and in unison so as to vary the compression spaces of the cylinders in direct ratio with the average pressures therein, said mechanism including a thrust member on the shaft and a thrust resisting member engaged by the thrust member, a dash-pot, said thrust resisting member constituting the movable element in the dashpot, a spring in the dash-pot acting on the said movable element, and a pressure pump for circulating fluid through the engine and dash-pot.

5. In an internal combustion engine, a shaft, a plurality of cylinders surrounding and disposed parallel to said shaft, a piston in each cylinder, constant, definite and positive driving connections between each piston and said shaft, said connections including a slant on the shaft and means carried by each piston engaging the slant, and automatically acting, resiliently actuated means, controlled by the average pressures in said several cylinders, for simultaneously shifting said shaft, slant and pistons to reduce to a minimum the compressive space in said cylinders under starting conditions, the piston stroke being maintained constant under all conditions of operation. A

6. In a multicylinder internal combustion engine in which gases of combustion are transferred from one to another of the plurality of cylinders, a plurality of cylinders,a piston in each cylinder, transmission mechanism whereby the pistons stand in constant, positive relation to an engine shaft, and means operating on the engine shaft and the pistons to move the shaft and pistons automatically and simultaneously uniform distances in unison so as to reduce the compression volume in each of said cylinders and thereby facilitate combustion therein prior to the commencement of effective transfer of said gases when the engine is started, the piston stroke being maintained constant under all conditions of operation.

7. In a multicylinder internal combustion engine in which gases of combustion are transferred from one to another of the plurality of cylinders, aplurality of cylinders, a shaft, :3. piston in each cylinder, transmission mechanism through which the pistons stand in constant, positive relation to the engine shaft, and mechanism automatically controlled by the pressure of the gases in said cylinders, for moving the engine shaft and pistons uniform' distances in unison so as to reduce the compression volume in each of said cylinders and thereby facilitate combustion therein'prior to the commencement of effective transfer of said gases when the engine is started.

8. In a multicylinder internal combustion engine in which gases of combustion are transferred from one to another of the plurality of cylinders, a plurality of cylinders, a shaft, 9. piston in each cylinder, transmission mechanism through which the pistons stand in constant, positive relation to the engine shaft, and mechanism automatically controlled by the pressure of the gases in said cylinders, said mechanism including spring means, equilibrating the pressure of said gases, for moving the engine shaft and pistons uniform distances in unison so as to reduce the compression volume in each of said cylinders and thereby facilitate combustion therein prior to the commencement of effective transfer of said gases when the engine is started.

9. In a multicylinder internal combustion engine in which gases of combustion are transferred from one to another of the plurality of cylinders, a plurality of cylinders, a shaft, a piston in each cylinder, transmission mechanism through which and a dash-pot for controlling the action of said spring means for moving the engine shaft and pistons uniform distances in unison so as to reduce the compression volume in each of said cylinders and thereby facilitate combustion therein prior to the commencement of eflective transfer of said gases when the engine is started.

10. In an internal combustion engine, a shaft, a plurality of cylinders, a piston in each cylinder, constant, positive driving connections between each piston and said shaft, and automatically acting means controlled by the average pressures in said several cylinders, for simultaneously shiftlng said pistons to reduce to a minimum the compressive space in said cylinders under starting conditions, the piston stroke being maintained uniform under all conditions of operation.

ANTHONY GEORGE MALDON MICHELL. 

